The overall objective of the proposed research is to gain a better understanding of the molecular defects associatd with abnormal proteoglycan production in certain mutant mouse systems. This proposed work builds on our previous familiarity and expertise in all aspects of biosynthesis of chondroitin sulfate proteoglycans, and extends now to an examination of the relationship between altered proteoglycan biosynthesis and pathological disturbances of connective tissue. For these purposes, two strains of mutant mice have been established in our laboratory. One, the brachymorphic mutant (bm/bm) involves a defect in sulfation, and as we have shown, appears to result from a deficiency in synthesis of the high energy sulfate donor - PAPS. Two interesting observations will be further explored in the proposed research 1) that both enzymes involved in PAPS synthesis, ATP-sulfurylase and APS-kinase, may be affected by themutation, and 2) that the defect appears to be more widespread but not universal, affecting sulfation of some other molecules in other tissues besides proteoglycans in cartilage, while other tissues are apparently not affected at all. To answer both of these questions, purified enzymes to which antibodies can be made are essential. In the other mutant mouse strain (cmd), a lethal defect which was reported to be caused by failure to synthesize proteoglycan core protein, is found. We have proposed experiments which should establish whether core protein is absent or abnormal in the cmd mutant. The ultimate intention in elucidating the biochemical defects in these systems is to subsequently utilize them as model systems for studies which will extend to certain human growth disorders, about which virtually nothing is known at the molecular level. Also, it is envisioned that these systems may be used to advantage for gene replacement stuldies, which would open up a new range of possibilities for study of metabolic defects on the whole animal level.